The ability of microorganisms to transform carbonitriles to corresponding amides was described in literature at the beginning of 70th years of the XX century. Nitrile hydratase enzyme catalyzing such reactions is inherent to a wide range of bacteria relating to various taxonomical groups. Representatives of the genus Rhodococcus are of practical interest with respect to the subject of the present specification. Large chemical and biotechnological companies of Japan, Korea, France, Russia, Germany, the USA and China use, inter alia, cells of strains belonging to this genus as effective biocatalysts for acrylamide production.
Despite deep investigations of the process of the enzymatic hydrolysis of nitriles to corresponding amides and considerable successes in the field of selection of strains producing nitrile hydratase, the industry demand for new biocatalysts has not dropped. This is caused, on the one hand, by the efficacy and ecological safety of biotechnological production of amides, in particular acrylamide, and on the other hand by a high cost of earlier patented strains and technologies. Therefore in recent years new microorganisms which were producers of a nitrile hydratase enzyme were isolated.
Known bacterial strains and methods for producing acrylamide using such strains, however, suffer from several drawbacks. Many strains are only capable of producing a maximum concentration of less than 40% of acrylamide, and therefore the use of such strains is limited.
Another disadvantage of certain strains is the components that are expensive and vary in composition, such as vitamins, peptone or yeast extract, must be included in their cultivation medium. Some strains exhibit only low nitrile hydratase activity. To increase activity, additional steps such as removal of oxygen from the culture broth together with the enzyme activation during several days may be required.
Some strains require a cultivation medium that contains toxic components. For instance, acetonitrile may be required in the cultivation medium, but acetonitrile is toxic, volatile, highly inflammable and expensive.